Hundreds of New South Wales Hunter region workers at coal haulage company Pacific National will walk off the job this week over a long-running industrial dispute.

The Rail Tram and Bus Union says the coal train drivers have serious concerns about wages and conditions, and are being bullied and intimidated by the company.

The stoppage will start at midday on Friday and run for 24 hours.

Union National Secretary Bob Nanva says the industrial action will affect the transportation of more than 300,000 tonnes of coal to the Port of Newcastle.

"We have seen no movement from the company on our entirely justifiable wage claims, nor around conditions such as drug and alcohol testing, which test for impairment rather than what someone might have done in their private time," he said.

"These are very important claims for our members ones that they do not want to take a backward step on."

He says Pacific National workers rejected a wage and conditions offer in December.

"Since the vote in December to reject the agreement we have seen the company try to bully threaten and harass the workforce into accepting an agreement they simply do not want," he said.

"We are saying its time for that campaign of harassment to end, for them to sit at the table, negotiate like adults and reach a reasonable outcome."

Pacific National Coal director David Irwin says the company has bent over backwards to finalise the enterprise agreement, including an offer to enter into binding arbitration with the Fair Work Commission.

Mr Irwin says because capacity to move coal is limited, the company will not be able to make up for the lost time.

"For every 24 hours we move well over 300,000 tonnes of coal for New South Wales, both into steelworks and power stations for domestic consumption, and into Port Kembla and Newcastle for export.

"That coal will not move, and in constrained coal chains it's capacity that's lost, that's not able to be caught up at a later time."

Free trade is the oldest argument in federal politics and the issue that literally defined the federation era but opposition exists to the TPP, courtesy of the Investor-State Dispute Resolutions clause.